1. Field of the Invention
The present invention relates to a plating technology and, particularly, to a method for plating flexible printed circuit boards.
2. Description of Related Art
Recently, flexible printed circuit boards (FPCBs) are widely used in portable electronic devices such as mobile phones, digital cameras and personal digital assists (PDA). In these electronic products, some parts may move relative to a main body. In such environment, FPCB can provide an electrical connection between the main body and the movable parts due to its excellent flexibility.
Nowadays, roll-to-roll process is employed for mass-producing FPCBs. In order to implement roll-to-roll process, a large sheet of raw material can be divided into a number of tape-shaped substrates. Sizes of tape-shaped substrates can be predetermined according to the sizes of the desired FPCBs. FIG. 6 shows a typical tape-shaped substrate 10. The tape-shaped substrate 10 includes a main region 14 for forming FPCB units 15, and two sprocket regions 11. The main region 14 is disposed along a lengthwise direction of the tape-shaped substrate 10. Two sprocket regions 111 are separately arranged at two sides of the main region 14. Each sprocket region 11 includes a number of sprocket holes 12 and a continuous copper layer 13 surrounding the sprocket holes 12. The sprocket holes 12 are disposed along the lengthwise direction of sprocket region 11.
In a roll-to-roll process, the sprocket holes 12 are used to mate with rollers to convey the tape-shaped substrate 10. The continuous copper layer 13 is provided to maintain the shape of each of the sprocket holes 12, so as to avoid deformations of the sprocket holes 12 during the conveying process. Regarding the tape-shaped substrate 10, the sprocket region 11 is located outside of the main region 14. After the FPCB units 15 have been molded, the sprocket region 11 is subject to be thrown away. However, during a plating process, metal material such as gold/nickel will be plated on the continuous copper layer 13. Thus, these valuable materials (e.g., gold/nickel) will be wasted when the sprocket region 11 is thrown away.
Therefore, a method for plating a flexible printed circuit board is desired to overcome the above shortcomings.